Women in their first pregnancy constitute ~40% of deliveries in the United States. Some will suffer complications such as preterm birth (PTB), preeclampsia, fetal growth restriction and stillbirth, which carry risks for both mother and fetus. The resultant perinatal morbidities and mortality can be exacerbated if these are not anticipated and If intervention Is not timely and/or appropriate. Though various clinical and biological characteristics have been linked to obstetric complications, several (race/ethnicity, socioeconomic status, prior pregnancy outcomes) have been consistently associated with many of these. Women in their first pregnancy lack crucial knowledge regarding prior pregnancy outcomes to guide obstetric management. Data to inform obstetric care of nulliparous women, and to identify appropriate candidates for interventional trials, are critically needed. Prevention of complications in the first pregnancy could impact subsequent gestations through avoidance of operative delivery and other adverse outcomes. The applicant Pis from CASE-MetroHealth Medical Center and Ohio State University have established records for obstetric research, especially which focused on PTB, and have collaborated together and with others in the conduct of multicenter observational and interventional studies. Both Pis have mentored junior investigators and developed research teams capable of contributing to the research planned in the multicenter Preterm Birth in Nulliparous Women network (The PBN Network). The applicant institutions share a history of mutual collaboration through the NICHD Maternal-Fetal Medicine Units (MFMU), and the Ohio Perinatal Quality Collaborative (OPQC) networks. The CASE and Ohio State University investigators have provided leadership in design and conduct of MFMU and OPQC network studies, and have participated in and led the administrative committees needed for the success of these groups. Both applicant institutions share the culture and resources needed to successfully complete observational and interventional studies in obstetric and neonatal care. We offer resources and expertise in fetal imaging, Doppler velocimetry, perinatal pathology, genetics and epidemiology. The PBN Network will bring important understanding to the prediction and prevention of complications in nulliparas. The applicant institutions possess the needed abilities and infrastructure to collaborate in the conduct of these studies that will directly impact clinical practice and inform future research. PUBLIC HEALTH RELEVANCE: First pregnancies represent approximately 40% of deliveries, and result in ~1.6 million deliveries annually in the United States. In nulliparous women, the risk of complications is difficult to determine due to the lack of information from prior pregnancies. This study will provide to caregivers, the clinical, ultrasound, patho- physiologic and biologic markers needed identify those at-risk for pregnancy complications including preterm birth, so that monitoring and interventions can be focused to prevent or reduce the impact of these, and to identify at-risk women who can be included in future interventional trials.